Modulatory adherent mononuclear cells have been defined in a number of human diseases and experimental animal models and may be important in the regulation of immunity. Suppression of the host response may be particularly relevant in opposing the clearing of infection. This study will evaluate immunomodulatory events in human tuberculosis emphasizing the role of adherent cells in regulatory phenomena which may predispose to progression of infection. Human peripheral blood mononuclear cells will be obtained from healthy volunteers and patients with tuberculosis for comparison of overall immune function using in vitro assays of T-lymphocyte, B-lymphocyte and macrophage activation. Then, adherent cells will be depleted and varying numbers of adherent lymphocytes and macrophages will be added to the responding population to study possible regulatory phenomena using the same assay systems. Finally, cell mixing experiments utilizing purified cell lines from donors with differing exposure history as regards tuberculosis will be used to corroborate immunoregulatory cell interaction. In addition to determining that a given adherent cell-type is regulating the immune response, its own state of activation and effect on other cell lines will be elucidated, permitting unravelling of the complexities and control mechanisms of immunity in tuberculosis. These studies may prove important in understanding the expression of tuberculous disease and have the potential to suggest new therapeutic approaches both in tuberculosis and diseases treated with immunoadjuvant agents.